CMSIS-DSP: Complex Dot Product

| CMSIS-DSP Version 1.4.7 CMSIS DSP Software Library

- Main Page
- Usage and Description
- Reference

All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
Functions
Complex Dot Product
Complex Math Functions

## Functions
void | arm_cmplx_dot_prod_f32 (float32_t *pSrcA, float32_t *pSrcB, uint32_t numSamples, float32_t *realResult, float32_t *imagResult)
| Floating-point complex dot product.
void | arm_cmplx_dot_prod_q15 (q15_t *pSrcA, q15_t *pSrcB, uint32_t numSamples, q31_t *realResult, q31_t *imagResult)
| Q15 complex dot product.
void | arm_cmplx_dot_prod_q31 (q31_t *pSrcA, q31_t *pSrcB, uint32_t numSamples, q63_t *realResult, q63_t *imagResult)
| Q31 complex dot product.

## Description

Computes the dot product of two complex vectors. The vectors are multiplied element-by-element and then summed.

The `pSrcA` points to the first complex input vector and `pSrcB` points to the second complex input vector. `numSamples` specifies the number of complex samples and the data in each array is stored in an interleaved fashion (real, imag, real, imag, ...). Each array has a total of `2*numSamples` values.

The underlying algorithm is used:

    realResult=0;
    imagResult=0;
    for(n=0; n<numSamples; n++) {
        realResult += pSrcA[(2*n)+0]*pSrcB[(2*n)+0] - pSrcA[(2*n)+1]*pSrcB[(2*n)+1];
        imagResult += pSrcA[(2*n)+0]*pSrcB[(2*n)+1] + pSrcA[(2*n)+1]*pSrcB[(2*n)+0];
    }

There are separate functions for floating-point, Q15, and Q31 data types.

## Function Documentation

void arm_cmplx_dot_prod_f32 | ( | float32_t * | pSrcA,
|  | float32_t * | pSrcB,
|  | uint32_t | numSamples,
|  | float32_t * | realResult,
|  | float32_t * | imagResult
| ) |  |

Parameters

  *pSrcA | points to the first input vector
  *pSrcB | points to the second input vector
  numSamples | number of complex samples in each vector
  *realResult | real part of the result returned here
  *imagResult | imaginary part of the result returned here

Returns
  none.

void arm_cmplx_dot_prod_q15 | ( | q15_t * | pSrcA,
|  | q15_t * | pSrcB,
|  | uint32_t | numSamples,
|  | q31_t * | realResult,
|  | q31_t * | imagResult
| ) |  |

Parameters

  *pSrcA | points to the first input vector
  *pSrcB | points to the second input vector
  numSamples | number of complex samples in each vector
  *realResult | real part of the result returned here
  *imagResult | imaginary part of the result returned here

Returns
  none.

Scaling and Overflow Behavior:

  The function is implemented using an internal 64-bit accumulator. The intermediate 1.15 by 1.15 multiplications are performed with full precision and yield a 2.30 result. These are accumulated in a 64-bit accumulator with 34.30 precision. As a final step, the accumulators are converted to 8.24 format. The return results `realResult` and `imagResult` are in 8.24 format.

void arm_cmplx_dot_prod_q31 | ( | q31_t * | pSrcA,
|  | q31_t * | pSrcB,
|  | uint32_t | numSamples,
|  | q63_t * | realResult,
|  | q63_t * | imagResult
| ) |  |

Parameters

  *pSrcA | points to the first input vector
  *pSrcB | points to the second input vector
  numSamples | number of complex samples in each vector
  *realResult | real part of the result returned here
  *imagResult | imaginary part of the result returned here

Returns
  none.

Scaling and Overflow Behavior:

  The function is implemented using an internal 64-bit accumulator. The intermediate 1.31 by 1.31 multiplications are performed with 64-bit precision and then shifted to 16.48 format. The internal real and imaginary accumulators are in 16.48 format and provide 15 guard bits. Additions are nonsaturating and no overflow will occur as long as `numSamples` is less than 32768. The return results `realResult` and `imagResult` are in 16.48 format. Input down scaling is not required.